1. Field of the Invention
The present invention relates to a metal mold for producing a synthetic resin molded product, particularly a thermoplastic resin molded product.
2. Description of the Prior Art
Conventionally, a producing method for a synthetic resin molded product has been well-known, in which a pair of male and female molds that are freely opened and closed are used, and the synthetic resin molded product is produced by clamping and compressing melted synthetic resin that has been supplied between the two molds.
However, in such a conventional method, the sliding faces or the contact faces of the paired male and female molds are placed along the outer circumferential line of the plane projection figure in the mold-clamping direction of a synthetic resin molded product to be obtained; consequently, burrs are produced along the outer circumferential portion of the molded product due to the melted synthetic resin entering between the sliding faces or the contact faces.
For this reason, problems are encountered in which: curved portions are not formed along the outer circumferential portion of the molded product, burrs tend to cause a cut in the hand of the worker and the product might be stuck during a line transportation, causing a jam; thus, in order to avoid these problems, an extremely time-consuming task, i.e. burr removing, is required.
Moreover, in order to form a hole in the molded product, a construction, in which a pin is put on the female mold or the male mold and the pin is allowed to contact the other mold, is generally used. However, in the conventional mold structure, the pin is only put in the same direction as the mold-clamping direction, which limits the positions of holes and the directions of holes.
In order to solve this problem, an upper-lower separation type metal mold for producing a synthetic resin molded product has been proposed, in which a first mold, a sliding mold that is allowed to slide relative to the mold, a second mold that is engaged with the siding mold and an extending device installed in the sliding mold, are provided (see Japanese Examined Patent Publication No. 16893/1991 (Tokukou-hei 3-16893).
However, in the mold of this type, the sliding mold and the second mold are fixed by the extending device, but the extending device tends to fail to sufficiently secure the sliding mold and the second mold depending on the molding conditions and types of the synthetic resin to be used.